Fibre reinforced cement

ABSTRACT

A fibre-reinforced cement product comprises a cement matrix containing at least 10% by weight of a pozzolana and alkaliresistant glass fibres containing zirconia.

Nib-99. AL) 116 EX umwu claws rawm 1 1 1111 3,852,082 Majumdar 1 1 Dec. 3, 1974 [5 FIBRE REINFORCED CEMENT 2.738.285 3/1956 Biefcld 106/99 3.704.147 11/1972 Hardy et a1. r. 106/57 [75] Invent: Amalend Mallumda" 3,736,162 5/1973 Chvalovsky et a1 106/99 Albans, England [73] Assignee: National Research Development FOREIGN PATENTS OR APPLICATIONS cm'poramn London England 390,123 6/1931 Great Britain 106/99 [22] Filed: July 26, 1972 467,159 8/1950 Canada 106/99 [21] Appl. No.: 275,421

Related US. Application Data Primary ExaminerDe1bert E. Gantz [63] Continuation-impart of Ser. No. 127,361, March 23, Assistant Examiner james Heuwege 1971, PaL 3 733 092 Attorney, Agent, or Firm-F1ynn & Fnshauf [30] Foreign Application Priority Data Aug. 5, 1971 Great Britain 36856/71 ABSTRACT [52] US. Cl. 106/99 [51] Int. Cl C04b 7/12 A fibr' o ced product comprises 21 ee- [58] Field of Search 106/99,D1G. l ment matrix containing at least 10% by weight of a pozzolana and alkali-resistant glass fibres containing [5 6] References Cited zirconia.

UNITED STATES PATENTS 2,446,990 10/1948 Schuetz 106 99 17 Claims, No Drawings FIBRE REINFORCED CEMENT This application is a continuation-in-part of application Ser. No. 127361 filed Mar. 23, 1971 now US. Pat. No. 3,783,092. This invention relates to glass fibrereinforced cementitious products and is an improvement or modification of the inventions described in U.K. Pat. Nos. 1200732 and 1243972.

Recent developments in the field of glass reinforced cement composites have resulted in the establishment of criteria for the compatibility of glass fibres with cementitious materials such as Portland cement and other types of cement in which the setting and hardening of the material depend on a reaction between calcareous and siliceous materials. These criteria including alkaliresistance have been described in our U.K. Pat. Nos. 1200732 and 1243972.

It has now been found, in accordance with this invention, that among the possible cements and glass fibres that may be used to give satisfactory composite materials an outstanding degree of water durability results from the combination of pozzolanic cements and glass fibres derived from glasses containing zirconia.

Pozzolanic cements are those containing a proportion of pozzolana which term is to be understood for the purposes of this application in the sense used by standard authors including especially R. H. Bogue The Chemistry of Portland Cement" (Rheinhold Publishing Corporation 2nd Edition, 1955) and F. M. Lea

The Chemistry of Cement and Concrete (Edward Arnold, 3rd Edition, 1970). Thus the term pozzolana although originally coined to signify a natural material of volcanic origin is now used to embrace artificial as well as natural materials which are silicate glassy materials capable of reacting with calcium hydroxide and thereby setting into a hard strong material. For example, material known as puly er i sed fuelash," a waste product which presents a disposal problem, has been found to be an excellent poggolana for the purposes of this invention. The natural o zzolana are abundant in various countries, eg ltaly, whereas among artificial pozzolanas certain glasses e.g. soda/lime/silica glasses may be mentioned.

Composite products of improved water durability have been obtained by the reinforcement of Portland cement containing at least l O percent pozzblana by weight, e.g., from about to about 50% or more, desirably at least and preferably to 45% eg pulverised fuel ash or other pozzolana with ,fib rgs of glasses'containing at least 6.0 mol ZrO preferably at least 9 mol ZrO including glasses based on the system SiO /ZrO /Na O, for example those described in U.K. application No. 1243972 and UK. application No. 37862/69.

Composite materials in accordance with this application may be produced by the techniques described in the above mentioned prior specifications and shaped as pipes, boards, sheets and other structures. Usually from 0. 5 to 10% by weight of glass fibre may be employed.

LII

Excellent results are obtained with 4 to 6% glass. 1n addition it has been found that a very desirable increase in the strength of the composites may be obtained by controlled heat treatment. This is a particularly important feature because of the necessity to achieve a suitable level of strength for the handling of the composite material at an early stage in manufacture and before the cement fibre bond has been well established. Furthermore, the heat treatment accelerates the attainment of stable properties and ultimate strength. In the case of cement boards prepared by the spray suction technique, a period of some days heating, e.g., 2 or 3 days under water at a temperature of at least 60C, e. g., 60 to C commenced at a time not less than about 5 hours after the casting of the board, gives rise to an acceptable bending strength, e.g., 2,500 psi. If more time is allowed to lapse after casting before heating is commenced, say 1 day or even up to 7 days, the strength of the matrix produced by the heating cycle is increased further. Higher temperatures may of course be employed, e.g., 80 to C, but if a temperature approaching too closely is used an undesirable level of attack on the glass fibre will result.

Typical results obtained with zirconia glasses reinforced matrices of ordinary Portland cement (OPC) and ordinary portland cement containing pulverised fuel ash (PFA), an Italian pozzolana or ground A glass (soda/lime/silica) are shown in the following Tables.

Table I gives the composition of the glass and quantities used:

TABLE 1 Code No. Glass Matrix Glass of Board Composition Content 7: by wt 1 A OPC 5.06 2 A OPC 40% PFA 5.46 3 B OPC 4.94 4 B OPC 40% PFA 5.17 5 C OPC 6 C OPC 40% PFA 5.12 7 A OPC 15% PFA 4.60 8 A OPC 25% PFA 5.03 9 A OPC 40% Pozzolana 5.17 10 A OPC 5.49 l 1 A OPC 40% PFA 5.34 12 B OPC 5.09 13 B OPC 40% PFA 5.62 14 A OPC 10% A glass powder 5.21

Table 11 shows modulus of rupture and impact strength figures obtained after specified period of storage under water at 18C.

3,852,082 3 4 TABLE 11 Continued Code No. DAYS of Board 7 days 28 days 1 yr. 2 yrs. 3 yrs.

3 3549 3836 2975 2650 4 2317 2486 2666 5 3696 3806 2500 6 2326 2512 3178 7 4572 4553 3257 8 4189 4135 3496 9 3970 5075 4990 4747 14 4630 5775 3620 4100 3970 Impact Strength 1 127 58 41 39 (inch 1bs./sq. in) 2 89 1 1 1 79 83 Table 111 provides corresponding results after water 20 Table V indicates the effect of the heat treatment retreatment at 60C. ferred to above. The composites are OPC 40% PFA TABLE 111 Code No. DAYS of Board 7 15 Modulus 5 3696 3470 2770 2:437 2363 2265 2083 1877 of Rupture 6 2326 2930 3136 2833 2916 2530 2516 2434 7 4572 4113 3022 1750 1479 8 4190 3547 3343 2956 2674 2386 1922 1839 10 4472 4732 3272 2850 1860 1515 11 2931 4370 4300 4004 3640 3535 3258 3112 12 3947 3695 2980 2556 2354 2255 2144 1684 13 2665 2868 2920 2822 2465 2450 2494 2320 Impact 5 82 67 48.5 35 24 20 16 13 Strength Table IV compares results obtained with 6.20, atypicontaining 5% fibres of glass A of Table 1 and initially cal zirconia glass and E-glass, a borosilicate glass. Com cured at 18C. The heat treatment at 60C immersed in posites were stored under water at 18C. water is given for 1 day or 2 day durations and the last TABLE IV Glass Particulars Content DAYS of Glass Matrix by wt. 7 28 360 Modulus of Rupture E glass OPC 5.3 4030 4000 3445 3000 2620 E glass OPC 40% PFA 5.26 2690 3260 3430 3120 2352 6.20 glass OPC 40% PFA 5.46 3268 3984 4266 4420 4566 impact Strength E glass OPC 63 27 I9 17 E glass OPC 40% PFA 73 76 32 13 0.20 glass OPC 40% PFA 89 87 89.5 111 column gives the figure obtained after storage at 18C in water subsequent to the heat treatment.

TABLE V Initial Strength 1 day 2 day l yr. storage Modulus of rupture 3420 4190 4470 Impact strength l 15 I02 92 Modulus of rupture 3420 4520 4250 Impact strength l 15 I05 95 Modulus of rupture 2100 2920 3270 impact strength 67 56 A particularly valuable embodiment of the invention is a fibre-reinforced Portland cement product containing from 35 to 45% by weight of pulverised fuel ash and reinforced with fibres of an alkali resistant glass containing at least 9 mol% ZrO and having a modulus of rupture after initial curing which increases with time.

\ I claim:

1. A fibre-reinforced pozzolanic cement product in which the cement matrix contains at least 10% by weight of a pozzolana and from 0.5 to 10% by weight of fibres which are alkali-resistant glass fibres comprising a silica/zirconia glass containing at least 6.0 mol percent of zirconia. 2. A cement product according to claim 1, in which the pozzolana content of the matrix is at least 3. A cement product according to claim 1, in which the pozzolana content of the matrix is at least 25%.

4. A cement product according to claim 1, in which the pozzolana content of the matrix is from 35 to 45%.

5. A cement product according to claim I, in which the pozzolana content of the matrix is at least 40%.

6. A cement product according to claim 1, in which the pozzolana is a natural pozzolana.

7. A cement product according to claim I, in which the pozzolana is pulverised fuel ash. 4

8. A cement product according to claim 1, in which the pozzolana is a soda/lime/silica glass.

9. A cement product according to claim 1, in which the glass is one based on the system SiO,/ZrO /Na O.

10. A cement product according to claim 1, in which the glass contains at least 65% SiO and at least 10% ZrO by weight.

11. A fibre-reinforced cement product according to claim 1 of improved water durability, said product having modulus of rupture and impact strength retentions of at least when tested before and after immersion in water at 50C. for 28 days.

12. A cement product according to claim 1 having a modulus of rupture of at least 3,500 pounds per square inch, an impact strength of at least 50 inch pounds per square inch, and which retains at least 80 percent of said properties when immersed in water at 50C. for 28 days.

13. A fibre-reinforced Portland cement product containing from 35 to 45% by weight of pulverised fuel ash and reinforced with from 0.5 to 10% by weight-of fibres which are fibres of an alkali resistant silica/zirconia glass containing at least 9 mol percent of ZrO and having a modulus of rupture after initial curing which increases with time.

14. A process of producing a fibre-reinforced cement product in which from 0.5 to 10% by weight of alkali resistant glass fibres comprising a silica/zirconia glass containing at least 6.0 mol percent of zirconia are incorporated in a cement matrix comprising Portland cement containing at least 10% by weight of a pozzolana.

15. A process of producing a fibre-reinforced cement product in which from 0.5 to 10% by weight of alkali resistant glass fibres comprising a silica/zirconia glass containing at least 6.0 mol percent of zirconia are incorporated in a cement matrix comprising Portland cement containing at least 1 0% by weight of a pozzolana and in which the resulting composite is subjected to a curing treatment at elevated temperature.

16. A process according to claim 15, in which the curing treatment is conducted in water at a temperature of at least 60C.

17. A process according to claim 16, in which the curing treatment is conducted at 60 80C for at least 2 days.

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UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION PATENT NO. I 3,852,082 D E 1 December 3, 1974 |NVENTOR(S) .AMALENDU JYOTI MAJUMDAR It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Title page, first column, under "[30]"- insert the following foreign priority data:

July 11, 1966 Great Britain 31025/66 February 2, 1967 Great Britain 5070/67 August 4, 1967 Great Britain 35901/67 April 3, 1969 Great Britain 17448/69.

Signed and Sealed this twenty-third Day Of September 1975 [SEAL] A ties t:

RUTH C. MASON C. MARSHALL DANN .-l1!vslr'ng Officer (mrmrisxr'rmcr 0f Parents and Trademarks UNITED STATES PATENT OFFICE 7 CERTIFICATE OF CORRECTION PATENT NO. 3,852,082 D TE I December 3, 1974 INVENTOR(5) i AMALENDU JYOTI MAJUMDAR It is certified that error appears in the above-identified patent and that said Letters Patent arehereby corrected as shown below;

Title page, first column, under "[30]":

insert the following foreign priority data:

July 11, 1966 Great Britain 31025/66 February 2, 1967 Great Britain 5070/67 August 4, 1967 Great Britain 3590l/67 April 3, 1969 Great Britain 17448/69.

t I Signed and Scaled this twenty-third D3) 0f September 1975 [SEAL] Arrest:

RUTH C. MASON C. MARSHALL DANN M- i g ffitl (vmmixsr'mrcr nj'larents and Trademarks 

1. A FIBRE-REINFORCED POZZOLANIC CEMENT PRODUCT IN WHICH THE CEMENT MATRIX CONTAINS AT LEAST 10% BY WEIGHT OF A POZZOLANA AND FROM 0.5 TO 10% BY WEIGHT OF FIBRES WHICH ARE ALKALIRESISTANT GLASS FIBERS COMPRISING A SILICA/ZIRCONIA GLASS CONTAIN ING AT LEAST 6.0 MOL PERCENT OF ZIRCONIA.
 2. A cement product according to claim 1, in which the pozzolana content of the matrix is at least 15%.
 3. A cement product according to claim 1, in which the pozzolana content of the matrix is at least 25%.
 4. A cement product according to claim 1, in which the pozzolana content of the matrix is from 35 to 45%.
 5. A cement product according to claim 1, in which the pozzolana content of the matrix is at least 40%.
 6. A cement product according to claim 1, in which the pozzolana is a natural pozzolana.
 7. A cement product according to claim 1, in which the pozzolana is pulverised fuel ash.
 8. A cement product according to claim 1, in which the pozzolana is a soda/lime/silica glass.
 9. A cement product according to claim 1, in which the glass is one based on the system SiO2/ZrO2/Na2O.
 10. A cement product according to claim 1, in which the glass contains at least 65% SiO2 and at least 10% ZrO2 by weight.
 11. A fibre-reinforced cement product according to claim 1 of improved water durability, said product having modulus of rupture and impact strength retentions of at least 80% when tested before and after immersion in water at 50*C. for 28 days.
 12. A cement product according to claim 1 having a modulus of rupture of at least 3,500 pounds per square inch, an impact strength of at least 50 inch pounds per square inch, and which retains at least 80 percent of said properties when immersed in water at 50*C. for 28 days.
 13. A fibre-reinforced Portland cement product containing from 35 to 45% by weight of pulverised fuel ash and reinforced with from 0.5 to 10% by weight of fibres which are fibres of an alkali resistant silica/zirconia glass containing at least 9 mol percent of ZrO2 and having a modulus of rupture after initial curing which increases with time.
 14. A process of producing a fibre-reinforced cement product in which from 0.5 to 10% by weight of alkali resistant glass fibres comprising a silica/zirconia glass containing at least 6.0 mol percent of zirconia are incorporated in a cement matrix comprising Portland cement containing at least 10% by weight of a pozzolana.
 15. A process of producing a fibre-reinforced cement product in which from 0.5 to 10% by weight of alkali resistant glass fibres comprising a silica/zirconia glass containing at least 6.0 mol percent of zirconia are incorporated in a cement matrix comprising Portland cement containing at least 10% by weight of a pozzolana and in which the resulting composite is subjected to a curing treatment at elevated temperature.
 16. A process according to claim 15, in which the curing treatment is conducted in water at a temperature of at least 60*C.
 17. A process according to claim 16, in which the curing treatment is conducted at 60* - 80*C for at least 2 days. 